I. Field of the Invention
The present invention relates to a semiconductor apparatus for controlling a large current at a high operating speed and, more particularly, to an improvement in the structure of the semiconductor apparatus.
II. Description of the Prior Art
Various types of power control equipment have been recently controlled with high precision and high efficiency using a high-power semiconductor device. A high-speed, high-power semiconductor device having a small power loss has been demanded in the field of power control equipment. When high-power switching is controlled by using the low-speed semiconductor device, a control frequency cannot be increased and is kept in an audio frequency region. Noise from such power control equipment causes discomfort to an operator. In addition to this disadvantage, a switching loss of the semiconductor device is so great that proper heat dissipation cannot be obtained. On the other hand, along with recent developments in semiconductor techniques, the switching speed of a high-power semiconductor device has been greatly increased. For example, a device for switching a current of several hundreds of amperes in a very short time interval of 0.1 .mu.sec or less has been developed. When this device is applied in the field of power control equipment, high-performance power control equipment can be provided wherein a switching loss is negligible even if its operating frequency is significantly higher than the audio frequencies.
Although such a semiconductor device is generally encapsulated in a package for practical application, thin lead wires are conventionally connected to control the electrodes of packed semiconductor devices such as a transistor and a thyristor. When such thin lead wires are used, an external signal supplied to the control electrode lead end of the semiconductor device is delayed due to the impedance of the thin lead wire. Furthermore, overshooting may occur due to an inductance component. These cause waveform distortion. In particular, when the high current thyristor of the high current transistor is turned off, the large current must be absorbed by their control electrodes. In this case, the influence of impedance and inductance of thin lead wires is typically observed, thus preventing high-speed operation. In semiconductor devices such as a static induction thyristor (SIThy) and a bipolar mode static induction transistor (BSIT), since a large number of electrons and holes are injected in the channel during the conducting state, injected electrons or holes must be absorbed by the control electrode from the channel region at the turn-off process. When the turn-off speed is increased, an instantaneous current flowing through the control electrode is increased.
In the conventional semiconductor apparatus, even if the semiconductor device is capable of controlling a large current with high speed operation, the impedance of the lead wires connected thereto is increased at the instance of high speed switching and a large voltage drop appears due to this impedance, and thus the operating speed of the device cannot be greatly increased.